SENSORY ADAPTATIONS OF BATS. I 59 



these peculiarities, since the angles and projecting ledges of the 

 caves would prevent a straight and continuous flight. Catching 

 insects on the wing would make agility count for more than en- 

 durance and steadiness, and hence the characteristic mode of flight 

 has been preserved. 



The migrations previously mentioned (p. 155) would seem to 

 indicate that individuals may travel five or six hundred miles 

 twice a year. The steady flight noticed by Howell ('08) in 

 diurnal migration may be taken as an indication that these 

 animals make long, continuous flights and have considerable 

 endurance. In this characteristic we find another analogy to 

 birds. 



A flying bat can change its course or check its momentum 

 very quickly. When it does not perceive a solid object that it is 

 approaching, it sometimes strikes its head while going full tilt 

 and falls down. Usually, however, an object is perceived before 

 actual contact takes place, and in that case the animal is always 

 able to check its flight and alight on the obstacle if it is too near 

 to turn aside and avoid it. 



The quick turns and dodges seem to be made by changing the 

 angle of the wings either antero-posteriorly or dorso-ventrally. 

 The interfemoral membrane and tail may act as a rudder, but a 

 bat from which they had been removed flew as well as before the 

 operation. 



A flying bat can alight on a vertical wall in several different 

 positions. Oldham ('05) states that the British Vespertilionidae 

 alight on vertical surfaces with the head upward and reverse 

 quickly after obtaining a foothold, while the lesser horseshoe bat 

 (family Rhinolophidae) reverses in the air and alights head down- 

 ward. Both of our common species of Aljotis, and I think all 

 of our other cave-inhabiting bats, can reverse in the air and 

 alight head downward although they do not always do so. 

 When flying against a window screen or some other object, not 

 perceived until it is almost touched, they alight head up, striking 

 with the anterior end of the body first and letting the posterior 

 end settle down. 



The reversal consists in a sidevvise dip with wing and head, the 

 hind limbs being brought forward and thrown upward at the 



